Recorded at one speaker binding posts using 20Kohm & 1Kohm resistors to adapt the signal to line-in levels for Delta 410 (http://www.hut.fi/Misc/Electronics/circuit...er_to_line.html). Needed to make sure that the speakers are sucking the amp dry *- attenuation was a bit too much for the line in (the sound is a bit grainy) - noise level was around ~60-70dB in Sound Forge 6, signal levels around -20dB, 24bit 88khZ. Removed DC offset, normalized to ~93%, resampled to 44.1 using Anti-Alias filter/4, noise shaped & dithered down to 16bit.

Before starting, how do we know that this is the amplitude diagram and not the phase diagram ?

That is an older version of the LMS (loudspeaker measurement system) software. When you clicked on the phase button (right of impedance) it would display the phase graph. The proggie didn't excel in usability, but that is the impedance graph in the link.

Sorry, I used 20kohm & 1kohm resistors (was not sure as I built that some 3 months ago to RMAA the modifications I did to the amp - no measurable anomalies (would need better soundcard) except for added crosstalk around -90dB) when using a 5W 100 ohm resistor as load (no speakers).

CAT5 (standard UTP Network cable): used 4 lenghts (with the outer jacket) of 4-twisted pair per speaker: so would be an equivalent to 24 gauge*16wires for one polarity... dunno how much that gets to...

However, there is no point in getting worried about cables if you don't have such a pathological case as mine: 4ohm nominal impedance, 86dB/W/m sensitivity & serious impedance swings so lots of current @constant voltage needed (no 2-way bookshelf speaker would exhibit such behaviour).

The infinity Kappa 9 I mentioned earlier is not my speaker, however it was the only impedance graph I could find for such a case. I guess my RSII's are somehow similar.

So it is quite a big gauge after all.24 AWG is 0.20 mm216x0.2=3.2 mm2, that is around 12 AWG.

This is surprising... Maybe recording the signal at the ampli plugs and comparing the 4 results (the two cables, speaker-side, and the two cables, ampli-side) could give more info. If the two ampli-side recordings are similar, the speaker-side recording that is the closest should be the best.

By the way, I find the idea of an attenuator for speaker - line connection strange. The author assumes that the output of an ampli is 3 to 20 Volts. This is true when the ampli is completely overdriven, and the speakers maybe broken.Actually, I plugged directly the speaker output of my ampli into the line input for my recordings, and I had to set the volume so that I was worried about the neighbours, because it was late, so as to reach a proper line in level.Your attenuator was 20:1, thus without it, you'd have got a signal 26 dB louder. You say that it was -20 dB, thus it would have clipped by 6 dB.

I recall again for everyone else : this experiment is DANGEROUS for your amplifier : a short circuit, a loose contact, a jack plugged off... and your ampli is fried !

unless it has protection for those situations, many amps have over-current protection so they don't get cooked if they're accidentally short-circuited. Would hate to find out the hard way though if I were unsure if it had that kind of protection.

- Although it should be the case - I can tell you that in practice it is not always that way. Prime example was my last MB which was getting random data errors from the VIA chipset - because of what i guess was interference the digital data was getting corrupted.

Just an aside: If your board doesn't work, its broken. No amount of interfernce you're going to get outside of a labratory (let alone your home) is going to effect your motherboard.

High freq. attenuation of CAT5 cable is quite probably due to high capacitance of this cable, together with low impedance of load at high frequencies. This can cause a high-frequency rolloff. For this reason, CAT5 cable would not be good for tough loads such as this.

So it is quite a big gauge after all.24 AWG is 0.20 mm216x0.2=3.2 mm2, that is around 12 AWG.

This is surprising... Maybe recording the signal at the ampli plugs and comparing the 4 results (the two cables, speaker-side, and the two cables, ampli-side) could give more info. If the two ampli-side recordings are similar, the speaker-side recording that is the closest should be the best.

By the way, I find the idea of an attenuator for speaker - line connection strange. The author assumes that the output of an ampli is 3 to 20 Volts. This is true when the ampli is completely overdriven, and the speakers maybe broken.Actually, I plugged directly the speaker output of my ampli into the line input for my recordings, and I had to set the volume so that I was worried about the neighbours, because it was late, so as to reach a proper line in level.Your attenuator was 20:1, thus without it, you'd have got a signal 26 dB louder. You say that it was -20 dB, thus it would have clipped by 6 dB.

I recall again for everyone else : this experiment is DANGEROUS for your amplifier : a short circuit, a loose contact, a jack plugged off... and your ampli is fried !

As KikeG said, the attenuation might be due to the high capacitance/low impedance (which would act as an RC filter? ) - twisted pairs for all length - (+that would add a meter or two to the effective length of the cable...).

For 111dB SPL / 95dB/1W/1m speaker sensitivity a rough calculation would yield 25W. For 86 dB/1W/1m & the same perceived loudness one would need around 200W. Go figure that I want a beefier amplifier just after doing that

So i'd need lots more amplifier power/voltage/amperage/whatever for same SPL (also taking in account the supposedly impedance swings which would need lots of current). The lowish sensitivity & impedance troubles is due to 2*10" woofers, 3*5" mid drivers and two tweeters to be driven through what is seems to be a major network of capacitors, transformer-type coils, shunt LC filters and long lengths of wire. However, the sound is pure bliss (okay, I'm going to the dark side here...)

I'll try to redo the test with amp side recordings next weekend. Ugh... I'd also use my smaller 3-way bookshelf speakers to provide data on 'speaker load/cables/amplifier matching'. Until then I'll keep kicking myself in the nuts for staying three months with CAT5 cable... as the difference while listening is humongous (at least that's what I'm hearing on the other side of the speaker).

Until then I'll keep kicking myself in the nuts for staying three months with CAT5 cable... as the difference while listening is humongous (at least that's what I'm hearing on the other side of the speaker).

It seems you have decided that big lamp cord sounds better that cat5 cable. Has this been established as a fact?

Some questions:

1. Pio2001 made an interesting graph comparing the signals to eachother. The signals are different, but which one is more transparrent? I believe the samples should be compared to the original instead of eachother.

2. The recording is made behind the speaker. Is this relevant to how the speaker sounds?

3. Does the signal cable from speaker terminal to line-in affect the sound?

4. A lossy codec + DSP operations was used to provide the source. I should prefer a lossless codec without any replaygain/DSP operations done as the source for such an experiment (just to be sure we are testing the right thing).

It seems you have decided that big lamp cord sounds better that cat5 cable. Has this been established as a fact?

Some questions:

1. Pio2001 made an interesting graph comparing the signals to eachother. The signals are different, but which one is more transparrent? I believe the samples should be compared to the original instead of eachother.

2. The recording is made behind the speaker. Is this relevant to how the speaker sounds?

3. Does the signal cable from speaker terminal to line-in affect the sound?

4. A lossy codec + DSP operations was used to provide the source. I should prefer a lossless codec without any replaygain/DSP operations done as the source for such an experiment (just to be sure we are testing the right thing).

No, CAT5 sounds worse in my particular case. With speakers which do not draw lots of current (eg. bookshelf or small 3-way) it may even sound better or there would be no measurable or audible difference.

1. The CAT5 sounds muffled & no dynamics. The lamp cord brought the sound close to my Sennheiser HD600.

2. Yes, it's what actually gets into the speaker as a signal.

3. I don't think so (10kOhms+ line in) versus 4 Ohms for speaker.

4. It's enough to test with a lossy codec. It would make a bigger difference with a full-bandwith (uncompressed lossless) encoding.

I won't do another test, as my amp got fried somewhere in the middle of the process... 3/6 output transistors gone (literally blew up), one driver transistor gone, two diode rectifiers, one trannie from the feedback circuit, two resistors that controlled the bias current and now I'm to emitter resistors which went gaga. Hope I pull it through somehow...

DO NOT CHANGE CABLES/DO ANY OPERATIONS ON YOUR AMP IF IT IS WORKING & TRIPPLE CHECK EVERYTHING BEFORE STARTING IT.

edit: it works 'ok' now but the side that blew gets too hot... back to the hacking table.

Sorry to hear about this.Either there was a short circuit somewhere, which is likely with thin coaxial cables, especially with one end stripped out for the speaker connection, or with the plugging-unplugging (center of the cinch accidentally in contact with any grounded metallic part), or even the line input muting (can be internally muted by short-circuiting it)... Either the capacity of the coaxial cable added to the speaker cable drove the output stage of the "audiophile-kind-sound-is-more-important-that-security" amplifier into positive feedback.

If all is repaired and one side is abnormally hot, there might still be partially burned transistors : try to play some pure sound at a loud level (but don't blow your speakers, it would be very annoying ! ), and watch for the hot channel to sound clipped.

Phew, I fixed it... turned out that the potentiometer that controlled the bias current was a little oxidized too due to high current that passed through when a diode blew, cleaned it, adjusted quiescent current as per the other channel setting & everything is OK now.

Cost: 15 euros + 8 hours of 'debugging'

Now to use banana plugs on the cables instead of bare coax wires for line input purposes... but some other time...

Horror pic here (23cm diameter for the transformer can in the middle; you can see on the right board two white resistors that replaced the old ones which caught fire)